diff --git a/structure/string_test.go b/structure/string_test.go
new file mode 100644
index 00000000..12f57ff7
--- /dev/null
+++ b/structure/string_test.go
@@ -0,0 +1,93 @@
+package structure
+
+import (
+	"github.com/ByteStorage/FlyDB/config"
+	_const "github.com/ByteStorage/FlyDB/lib/const"
+	"github.com/ByteStorage/FlyDB/lib/randkv"
+	"github.com/stretchr/testify/assert"
+	"os"
+	"testing"
+	"time"
+)
+
+var err error
+
+func initdb() *StringStructure {
+	opts := config.DefaultOptions
+	dir, _ := os.MkdirTemp("", "TestStringStructure_Get")
+	opts.DirPath = dir
+	str, _ := NewStringStructure(opts)
+	return str
+}
+
+func TestStringStructure_Get(t *testing.T) {
+	str := initdb()
+
+	err = str.Set(randkv.GetTestKey(1), randkv.RandomValue(100), 0)
+	assert.Nil(t, err)
+	err = str.Set(randkv.GetTestKey(2), randkv.RandomValue(100), 2*time.Second)
+	assert.Nil(t, err)
+
+	value1, err := str.Get(randkv.GetTestKey(1))
+	assert.Nil(t, err)
+	assert.NotNil(t, value1)
+
+	time.Sleep(3 * time.Second)
+
+	value2, err := str.Get(randkv.GetTestKey(2))
+	assert.Equal(t, err, ErrKeyExpired)
+	assert.Nil(t, value2)
+
+	_, err = str.Get(randkv.GetTestKey(3))
+	assert.Equal(t, err, _const.ErrKeyNotFound)
+}
+
+func TestStringStructure_Del(t *testing.T) {
+	str := initdb()
+
+	err = str.Set(randkv.GetTestKey(1), randkv.RandomValue(100), 0)
+	assert.Nil(t, err)
+
+	err = str.Del(randkv.GetTestKey(1))
+	assert.Nil(t, err)
+
+	_, err = str.Get(randkv.GetTestKey(1))
+	assert.Equal(t, err, _const.ErrKeyNotFound)
+}
+
+func TestStringStructure_Type(t *testing.T) {
+	str := initdb()
+
+	err = str.Set(randkv.GetTestKey(1), randkv.RandomValue(100), 0)
+	assert.Nil(t, err)
+
+	keyType, err := str.Type(randkv.GetTestKey(1))
+
+	TypeString := "string"
+	assert.Equal(t, keyType, TypeString)
+	assert.Nil(t, err)
+}
+
+func TestStringStructure_StrLen(t *testing.T) {
+	str := initdb()
+
+	err = str.Set(randkv.GetTestKey(1), randkv.RandomValue(100), 0)
+	assert.Nil(t, err)
+
+	strLen, err := str.StrLen(randkv.GetTestKey(1))
+	assert.Nil(t, err)
+	assert.Equal(t, strLen, 112)
+}
+
+func TestStringStructure_GetSet(t *testing.T) {
+	str := initdb()
+
+	err = str.Set(randkv.GetTestKey(1), randkv.RandomValue(100), 0)
+	assert.Nil(t, err)
+	value1, _ := str.Get(randkv.GetTestKey(1))
+
+	value2, err := str.GetSet(randkv.GetTestKey(1), randkv.RandomValue(100), 2*time.Second)
+	assert.Nil(t, err)
+	assert.NotNil(t, value2)
+	assert.Equal(t, value1, value2)
+}